EP2281009A1

EP2281009A1 - Process and apparatus for preparing biopolymers

Info

Publication number: EP2281009A1
Application number: EP09749629A
Authority: EP
Inventors: Bernhard Stützle; Pierre-Alain Fleury
Original assignee: List Holding AG
Current assignee: List Holding AG
Priority date: 2008-05-22
Filing date: 2009-05-20
Publication date: 2011-02-09
Anticipated expiration: 2029-05-20
Also published as: KR101326293B1; EP2281009B1; CN102083864A; JP2011521058A; ES2395701T3; CN102083864B; BRPI0912876A2; JP5615266B2; WO2009141139A1; US20110105716A1; CA2725028A1; KR20110021914A

Abstract

In a method of treating viscous products, particularly for the implementation of polymerization operations, more particularly for the homopolymerization or copolymerization of biopolymers, where monomer(s) and/or catalysts and/or initiators are fed to a backmixed mixing compound (1), in particular having a length/diameter ratio of 0.5—3.5, more particularly a process corresponding to a stirred tank cascade of 2-5 stirred tanks in series, and the product is supplied with heat and is backmixed with product that has already reacted, and the reacted product is taken off from the mixing compound (1), the product is to be heated in the mixing compound (1) up to its optimum processing temperature or boiling temperature or sublimation temperature, parts of the product are to be evaporated, and hence the exothermic heat of the product and excess mechanical introduction of heat are absorbed by means of evaporative cooling.

Description

METHOD AND DEVICE FOR PRODUCING BIOPOLYMERS

The invention relates to a process for the preparation of biopolymers, in particular for carrying out polymerization processes, in particular for the homo- or copolymerization of biopolymers, wherein monomer (s) and / or catalysts and / or initiators a back-mixed kneader, in particular with a length / diameter ratio of 0 , 5-3.5, added to the product heat and remixed with already reacted product and the reacted product is discharged from the mixing kneader, and a device therefor. The invention also relates to two-stage processes which combine polymerization processes with a downstream degassing / demonomerization / devolatilization stage. STATE OF THE ART

A significant portion of polymerization reactions, particularly for the preparation of homo- and co-polymeric biopolymers, such as PLA (polylacticacid), PHB (polyhydroxybutyrate), PHA (polyhydroxyalkanoate), polydextrose, biopet, starch, cellulose, kitins, and proteins, are commercialized as "slurry or solution process" in one or more cascaded continuously operated, back-mixed vertical stirred tank reactors, so-called "CSTR" continuous stirred tank reactors. These stirred tank reactors have the task as homogeneously as possible to distribute the monomers, the catalysts and initiators in a solvent / diluent at precisely defined Prozeßbedingungeni such as temperature and pressure so that the reaction proceeds in a controlled manner, a uniform product quality with the desired molecular weight and also controls the heat of reaction becomes. The problem with these stirred tank reactors is that only products with a low apparent viscosity or melt viscosity can be processed.

As the concentration of the polymer in the solvent / diluent increases, the apparent viscosity of the reaction mass increases such that the stirrer eventually can not generate sufficient convective flow. The consequence of this is an inhomogeneous distribution of the monomers. This leads to lump formation, poor molar mass distribution, caking, local overheating up to the uncontrollable reaction sequence of the entire reactor contents.

Another problem of stirred tank reactors is the foaming or a strong swelling of the product mass in the case of individual products, which can lead to blockages and closures on the dome exhausts.

The above-mentioned process hazards lead to stirred tank reactors with a large excess of solvent / diluent up to about 90% of the Operated reaction mass or in bulk polymerizations because of high viscosities only limited sales, often only less than 50%, can be achieved. As a result, additional process steps for mechanical / thermal separation of the diluent or the solvent / monomer or. to post-reaction (increase the chemical conversion rate) necessary.

This is usually done in dewatering screws, evaporation and drying systems and maturing tanks. They mean high investment, energy and operating costs. There are also new polymers that can not be processed with "Water Stripping Process"!

Bulk polymerizations or copolymerizations are also carried out continuously in single- or multi-shaft extruders (e.g., from Werner Pfleiderer, Buss Kneader, Welding Engineers, etc.). These devices are designed for high viscosity polymerizations in the viscous phase. They are designed as continuous plug flow reactors and accordingly have a large L / D ratio of> 5 to about 40.

Here are the following problems:

a) In slow polymer reactions with reaction times> 5 minutes, during which the reaction mass remains in the liquid state for a long time, the plug flow can not be maintained. The widely differing theological properties between the monomers and polymers prevent uniform product transport, resulting in undesirable quality variations.

b) The strong exothermicity of many polymerization processes as well as the mechanically dissipated kneading energy often make it necessary to dissipate these energies effectively and efficiently via evaporative cooling. In this case, part of the monomer or of the mixed solvent / diluent is evaporated, condensed in an external condenser and the condensate is returned to the reactor. Due to the -A-

large UD ratio and the design-related large screw cross-section are available for the deduction of vapors only very limited free cross-sectional areas. This leads to unwanted entrainment of polymers in the Domabzüge, the vapor lines and / or in the reflux condenser and as a result to blockages / closures.

c) In the production of (co) polymers of several different monomers is aggravating added that evaporates evaporative cooling mainly the monomer with the lowest boiling point, so that adjusts a shift in the monomer concentrations in the reactor, especially in the region of the inlet opening the condensate reflux. This is usually undesirable.

d) Another disadvantage is that the free product volume of screws for mechanical design reasons is limited to about 1, 5 m3, so that at

Reactions with residence times> 5 minutes only low throughputs can be achieved, which in turn requires the installation of several parallel lines with correspondingly high investment and operating costs.

Another possibility for carrying out bulk polymerizations up to high conversions is described in US Pat. No. 5,372,418. Here, co-rotating or counterrotating multi-screw extruders with non-intermeshing, oppositely-conveying screws or screw pairs are described for the polymerization of the monomers by back-mixing with the polymer in the viscous phase. These apparatuses are basically capable of carrying out polymerization processes up to high conversions and at the same time avoiding the previously described disadvantages a) (collapse of the plug flow) and c) (formulation displacement by reflux) from the plug flow extruder. However, the previously described problems b) (reduced free cross-section) and d) (size) remain unsolved. Og. Processes are also carried out in so-called mixing kneading, in which the product is transported by appropriate kneading and transport elements from an inlet to an outlet and at the same time brought into intensive contact with the heat exchange surfaces. Such mixing kneaders are described, for example, in DE-PS 23 49 106, EP 0 517 068 A1 and DE 195 36 944 A1.

TASK

Object of the present invention is the o.g. To carry out processes in a concentrated, higher-viscosity phase, to optimize the corresponding device and, above all, to accelerate the process steps and to increase the product quality or to expand the product range.

SOLUTION OF THE TASK

To solve the problem, on the one hand, that the product is heated in the mixing kneader to a certain processing temperature at which evaporate under the prevailing controlled operating pressure (pressure, atmosphere or vacuum) parts of the product and thus the exothermicity of the reaction mass as well as in the viscous reaction mass dissipated kneading energy can be effectively and efficiently absorbed by evaporative cooling. The operating conditions (heating temperature, operating pressure, mixer kneading degree, kneader shaft speed, etc.) are chosen so that whenever possible a quasi-balanced energy balance is achieved, which then allows an advantageous extrapolation of the method solely on the required for the process execution dwell time , The vaporized product (s) is (are) condensed and recycled specifically to the reaction mass (reflux condensation).

Since the wetted product surface is much larger than the apparatus contact surface of the mixing kneader, the condensate can act as a film over the entire

Distribute surface of the product and so to an efficient and homogeneous Contribute cooling effect. The open over the entire process space length gas space of the mixing kneader allow the evaporation of the (s) monomer (s) and the targeted recycling of the condensate, preferably in the feed area and / or the area with high reactivity.

Depending on the product, the optimum processing temperature is set by adjusting the operating pressure prevailing in the mixing mixer.

In a further embodiment of the method for which self-protection is sought, but which can be carried out particularly effectively in connection with the method just described, the back-mixing of the product should be carried out until a predetermined viscosity of the product and this viscosity by continuous addition of further monomer and / or catalysts and / or initiators are maintained.

A low viscosity shows the operator of a corresponding mixing kneader that only or substantially monomer is in the mixing kneader, which is low viscosity / low viscosity. The more the polymerization proceeds, the more the viscosity of the reaction mass increases. When a predetermined viscosity of the product is reached, this is a signal that a certain percentage of the product has now converted to polymer. This is a signal to operate the mixing kneader in a continuous process in such a way that the viscosity and thus the conversion or degree of polymerization remain the same. This is essentially determined by means of the kneader shaft torque, which is a function of the viscosity of the reaction mass at a constant mixing kneading degree of filling, and / or of the product temperature profile over the process space length of the mixing kneader.

Example 1 :

For example, PLA (Polylacticacid) can be used in the mixing kneader in an optimum processing temperature range of 175 to 1900C, under inert atmosphere, light weight Overpressure on nitrogen or an operating vacuum of 40 - 100 mbar abs. be prepared by adding the monomer lactide and the catalyst solution via a so-called "ring-opening" polymerization.

Below this optimum temperature range, the viscosity of the formed PLA increases drastically, whereby the kneader shaft torque increases sharply and increasingly mechanical Knetwärme is dissipated into the reaction mass. Above the optimum temperature range there is an increasing risk of thermal product damage and / or depolymerization with temperature and residence time.

Operation under light nitrogen overpressure has the advantage of excluding the possibility of uncontrolled entry of atmospheric oxygen or humidity damaging the reaction system; the operation under vacuum has the advantage of higher cooling effect by increased evaporation activity.

The monomer stream lactide (and the smallest amount of micro-mixed catalyst solution) is fed continuously in a molten state at temperatures above 115 ⁰ C to the mixing kneader. The micromixing of the molten lactide stream with the catalyst solution usually takes place by means of static mixers or "tube in tube mixers" shortly before entering the mixing kneader Micro mixing is a prerequisite for optimum reactivity and homogeneous product quality, as well as for stable process control micro-mixed feed is immediately mixed into the present in the mixing kneader, already in the feed partially converted, higher viscosity reaction mass, at usual product temperatures around 175-18O ⁰ C. The inflow is thus from the beginning in the mixing kneader ideal conditions and reaction temperatures above 140 ⁰ C, the spontaneous The exothermicity of the polymerization reaction and the mechanical heat of kneading dissipated in the heat cover the heating of the feed stream, and excess heat is transferred via evaporative cooling (evaporation and reflux condensate) ion of the monomer lactide) effectively to balance the energy balance. The heat transfer to the product via the contact surfaces of the mixing kneader heated with about 175-19O ⁰ C hot heat transfer oil or steam is negligible in the energy balance due to the small temperature differences of product / reaction mass and heating medium. The heat transfer is important only during start-up phases, as long as the required process heat can not be introduced via the mechanical kneader performance due to excessively low viscosities.

The product temperature profile in the mixing kneader can be depending on freely selectable parameters such as operating pressure, agitator shaft, filling ratio and product throughput (monomer and catalyst solution), ideally at the values set from 175-180 ⁰ C at the entry and at the discharge 180-190 °. This rising product temperature profile reflects increasing viscosity and increasing conversion to PLA in the mixing kneader for discharge. This makes it clear that the mixing kneader is not an ideally backmixed system, but that the behavior of a stirred tank cascade corresponds to about 3 to 5 stirred kettles connected in series.

The conversion rates reach up to about 90 - 96% PLA with a narrow molar mass distribution (polydispersity about 2). The required residence times in the mixing kneader are, depending on the desired molar mass and catalyst solution / concentration, 20 to 50 min.

Example 2:

The same device and process control with correspondingly adapted parameters are also suitable in the case of the production of PLA from the monomer lactic acid (lactic acid) via the polycondensation reaction.

By this method according to the invention the advantage is achieved, even high to very high melt viscosities can be processed efficiently and safely, and thus For example, in the case of polymer reactions to be able to achieve high conversion rates in one step and in a single mixing kneader. During the viscous mass process, phenomena that occur, such as extreme foaming and / or excessive swelling of the viscous product mass over very good interfacial renewal rates in the mixing kneader, are effectively suppressed.

In the mixing kneader, in addition to polymer reactions, the evaporation of polymer solutions can also be carried out efficiently. The evaporation energy required for the evaporation of large amounts of solvents is accordingly maximized by the combination of contact heat and above all high mechanically dissipated kneader heat (shearing). The possibility of keeping the product temperature constant or limiting it above the evaporation of solvent or monomers allows a high degree of freedom with respect to the regulation of the mechanical kneader heat over the speed (shear rate) and the degree of filling of the mixing kneader.

If, in a preferred embodiment, a second mixing kneader, extruder, flash pot or the like is arranged downstream, degassing or demonomerization / devolatilization also takes place therein. For example, in such a second mixing kneader or extruder, the product may be subjected to a plug flow by a corresponding geometry of the kneading elements. In this second process step, residual evaporation, which is often restricted by substances, takes place at very low residual contents of solvents and / or monomers, which is why preference is given here to using two-shaft mixing kneaders, which are described in the prior art. Flashpots may be particularly suitable for products where degassing or demonomerization / devolatilization is spontaneous and rapid, and which has sufficient fluidity, for example, to feed an underlying gear pump for subsequent granulation.

For mixing kneaders with plug flow property is essential that the surface / interface of the product is renewed as quickly as possible, because of this surface the liquid evaporates. Since the evaporation points retreat more and more into the gutter interior, the product surface must be permanently renewed by intensive kneading. Furthermore, a good product temperature control is necessary.

Above all, the concern of creating the greatest possible product / gas interfaces can be taken into account by dividing or comminuting the product prior to entry into the second mixing kneader / extruder / flash pot, for example, a corresponding perforated plate or a nozzle with a high Number of nozzle holes accomplished. If the product is pressed through a perforated plate by means of, for example, a gear pump after discharge from the first mixing kneader, it passes in strands (spaghettiform) into the second mixing kneader / extruder / flash pot. The second mixing kneader / extruder / flash pot is preferably run under low vacuum and maximum product temperature.

The discharge of the viscous polymer composition is accomplished by means of a twin screw with forced delivery integrated horizontally or vertically on the mixing kneader. This in turn feeds a directly downstream gear pump whose speed can be controlled so that the degree of filling and thus the Produktverweilzeit remain constant in the mixing kneader. The product supply to the gear pump is carried out under constant supply pressure via a speed control of the twin screw.

As a controlled variable for the speed control of the gear pump is the torque of Mischkneterwelle.

Example:

For demonomerization of the PLA mass formed in the first mixing kneader with a

Residual content of 4 - 10% monomeric lactide, this mass is by means of gear pumps via perforated plates and / or adequately formed nozzles a second mixing kneader /

Extruder / Flashpott fed, ideally under vacuum of <50 - 10 mbar abs., or even better under high vacuum <10 - 0.5 mbar abs. is operated. This ideally at a maximum allowable product temperature from 190 to 210 ⁰ C. The dwell time is as short as possible to hold on to and / or avoid product damage "chemical replica" of monomer lactide.

DESCRIPTION OF THE FIGURES

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing; this shows in its single figure a schematic representation of a system according to the invention for treating viscous products, in particular for carrying out polymerization reactions and subsequent degassing, demonomerization or devolatilization processes.

In a single-shaft or two-shaft, surrounded by a heating jacket 6 Mtschkneter 1 with back mixing mixing shaft geometry, which is filled with partially reacted product, continuously monomer (s), catalysts, initiators and possibly small amounts of solvent via corresponding metering devices 2 are continuously added and remixed in the process chamber , This is indicated by the dashed circle 10. The mixing kneader 1 is not ideally remixed, but in practice has a behavior which corresponds to that of a stirred tank cascade with 2 to 5, typically with 3 to 4 stirred tanks in series. This behavior agrees well with the number / division of chambers formed by the disks / disk elements / disk segments 13 mounted on the shaft (s) 12. Static kneading counter-elements 11 in the case of single-shaft mixing kneader or the dynamic kneading bar elements 13 mounted on the slices mesh with one another and cause intensive mixing and kneading of viscous masses. Here, the term "chamber" is not a closed room to understand, but open communicating with each other cells.

The viscosity of the reaction mass in the mixing kneader 1 is adjusted by the choice of the reaction system, the catalyst concentration, the throughput, the temperature, the pressure, etc., so that the product is directly degassed / demonomerized in a subsequent, second mixing kneader / extruder / flash pot 4 / is devolatilized, or the unreacted monomer in a subsequent apparatus, for example, a maturation tank, can be reacted. Processing temperature and operating pressure in the mixing kneader are preferably chosen so that adjust product viscosities that allow a limited mechanical heat input and / or that the monomer excess or the solvent content is in the boiling range. The corresponding temperature range depends on the polymer itself.

With this method just described, it is possible to dissipate the heat of reaction and the dissipated kneading energy by the evaporation of the solvent / monomer. This vapor is condensed in a reflux condenser 5 placed directly on the mixing kneader 1 and returned to the reaction mass. Several reflux condensers can also be distributed over the length of the mixing kneader 1. In particular, it is conceivable; that each chamber is assigned a reflux condenser. Incidentally, the condensation can also be realized externally, and the condensate can then be metered back into the reaction mass at specific points, preferably in the inlet and middle regions of the mixing kneader, with different nozzles. Due to the small L / D (length / diameter) ratio of preferably 0.5 to 3.5 of the mixing kneader 1, the refluxing condensate is optimally evenly mixed back into the reactor without targeted recycling, which in previously used backmixing extruders with a large L / D ratio represents a big problem.

The back-mixed mixing kneader 1 can travel under vacuum, atmospheric or under pressure. For polymerization systems operated with vacuum, a valve 23 is opened and the line 24 is connected to a vacuum pump. In this way, leakage gas flows and inert gas deposits are withdrawn, but the monomer condenses almost completely in the reflux condenser 5 and is returned to the reaction mass in the mixing kneader 1. For polymerization systems which are operated at atmospheric pressure, the valve 23 is opened and the line is left under these atmospheric conditions. For polymerization systems which are operated at pressures higher than ambient pressure, the system pressure is preferably regulated to a specific value with an inert gas (eg nitrogen), which is done by means of a valve 14. The valve 23 is closed in this case.

Example:

At PLA, the optimum processing temperature range is for the

Polymerization reaction at 175-190 ⁰ C, depending on the desired molecular weight of the PLA and depending on the product temperature profile, the specific kneader shaft torque between 20 - 45 Nm / liter process space total volume at a filling level of about 70%.

The operating pressure can be adjusted accordingly freely, so that the

Evaporation activity of the monomer lactide (evaporative cooling with reflux condensation) the higher or lower mechanical Knetwärmeentrtrag

Takes into account.

The reflux condenser is preferably heated with a heating medium of 110-140 °, at temperatures which allow a very complete condensation of the lactide vapors at the exchange surfaces, but which are still well above the solidification temperature (or melting temperature) of the monomer lactide and thus a liquid Guarantee reflux.

The reaction product / the viscous mass is at the discharge end of the mixing kneader by means of an integrated discharge device 3, a so-called discharge

Twin screw with forced conveying, which can be vertically but horizontally positioned, subtracted. This in turn feeds a directly downstream gear pump whose speed can be controlled so that the degree of filling and thus the

Product residence time in the mixing kneader remain constant. A constant controlled mixing kneading degree of filling is, in addition to the constant throughput predetermined by the metering units, an absolute necessity for ensuring process stability and stability to ensure uniform product properties. As a controlled variable for the speed control of the gear pump is a suitable measuring device 8 for the degree of filling, for example, the torque at the Mischkneterwelle, the weight of Mischkneter- product content (hold-up), the radiometric Füllgradsmessung etc. The product feed to the gear pump is carried out under constant supply pressure via a speed control of the twin screw.

The gear pump 17 is followed by a perforated plate or nozzle plate 18, through which product from the discharge device 3 can be introduced spaghetti-like into the second mixing kneader / extruder / flash pot 4. An arrow 20 between the gear pump 17 and the perforated plate or nozzle plate 18 indicates that gaseous or liquid stripping agents can also be added to the subsequent degassing support or additives, for example reaction stoppers, stabilizers, etc. in this area. Stripping agents cause a burst when tearing into the second mixing kneader / extruder / flash pot, tearing of the product surfaces and thus an improved mass transfer.

The second mixing kneader / extruder 4 is associated with a motor M, via which one or more stirring shaft / n 21 are driven with stirring / kneading elements 22. The Stirrwellengeometrie is designed so that a plug flow with a narrow residence time spectrum (corresponding to 10-16 cascaded stirred tanks) or a more or less pronounced backmixing (corresponding to 2 to 5 series stirred reactors) results. Further, the mixing kneader / extruder 4, one or more Brüdendom (s) 19 are placed, on the / can be deducted to be evaporated products (monomers, solvents, stripping agents, etc.).

Analogous to the mixing kneader 1, a further discharge screw 25 and a gear pump 26, which can supply the necessary pressure for the granulation of the end product, adjoin the mixing kneader / extruder 4.

Claims

claims

1. A process for the treatment of viscous products, in particular for carrying out polymerization processes, in particular for the homo- or copolymerization of biopolymers, wherein monomer (s) and / or catalysts and / or initiators a back-mixed mixing kneader (1), in particular with a

Length / diameter ratio of 0.5 - 3.5, added, in particular a behavior that corresponds to a stirred tank cascade of 2 - 5 series stirred tanks, the product supplied heat and remixed with already reacted product and the reacted product is discharged from the mixing kneader (1) .

characterized,

that the product in the mixing kneader (1) heated to its optimum processing temperature or boiling temperature or sublimation, vaporizes parts of the product and thus an exotherm of the product and excess mechanical heat input is absorbed by evaporative cooling.

2. The method according to claim 1, characterized in that the vaporized parts of the product, in particular in the polymerization of biopolymers such as PLA, PHA, PHB, etc. completely or at least partially condensed and recycled as condensate back into the mixing kneader for cooling the remaining product become.

3. The method according to claim 2, characterized in that the return to the mixing kneader (1) takes place at the point at which the main evaporation is carried out.

4. The method according to at least one of claims 1 to 3, characterized in that the processing temperature or boiling temperature or sublimation temperature is adjusted by changing the pressure in the mixing kneader (1) to a predetermined value.

5. The method according to at least one of claims 1 to 4, characterized in that for the removal of vapors in the mixing kneader (1) a vacuum is built up.

6. A process for the treatment of viscous products, in particular for carrying out polymerization processes, in particular for the homo- or copolymerization of

Biopolymers, wherein monomer (s) and / or catalysts and / or initiators a back-mixed mixing kneader (1), in particular with a

Length / diameter ratio of 0.5 - 3.5, added therein are remixed with already reacted product and the reacted product is discharged from the mixing kneader (1), characterized in that the back-mixing takes place until reaching a predetermined viscosity of the product, and this viscosity is maintained by the continuous addition of further monomer and / or catalysts and / or initiators.

7. The method according to at least one of claims 1 to 6, characterized in that the product is vaporized by energy input consisting of mechanical kneading and / or heat transfer over the contact with Kneterwärmeaustauschflächen to close above the breakpoint of the evaporation rate and in the so pre-evaporated viscous Product bed continuously new low-viscosity product solution is mixed in such a way that the evaporation rate remains above the breaking point.

8. The method according to claim 7, characterized in that a kneading energy is influenced by changing the rotational speed and / or the degree of filling of the mixing kneader (1).

9. The method according to at least one of claims 1 to 8, characterized in that the product in the mixing kneader (1) is continuously mixed back.

10. The method according to at least one of claims 1 to 9, characterized in that the product continuously discharged from the mixing kneader (1) and in a second mixing kneader or extruder or Flashpott (4) is entered.

11. The method according to claim 10, characterized in that the product is heated during discharge from the mixing kneader (1) before it enters the second mixing kneader or extruder or flash pot (4).

12. The method according to claim 10 or 11, characterized in that the product in the second mixing kneader or extruder (4) is subjected to a plug flow or a backmixing.

13. The method according to claim 12, characterized in that the product in the mixing kneader or extruder (4) is subjected to a large Oberflächenemeuerung and good product temperature control.

14. An apparatus for the treatment of viscous products, in particular for carrying out polymerization processes, in particular for the homo- or copolymerization of biopolymers with a continuously back-mixed mixing kneader (1), in particular with a length / diameter ratio of 0.5 - 3.5, for receiving Monomer (s) and / or catalysts and / or initiators which are backmixable with already reacted product, and a discharge device (3) through which the reacted product from the mixing kneader (1) can be discharged, characterized in that the mixing kneader (1) is divided into two to five, preferably in three to four chambers, in which the backmixing takes place.

15. An apparatus for the treatment of viscous products, in particular for carrying out polymerization processes, in particular for homo- or Copolymerization of biopolymers with a continuously back-mixed mixing kneader (1), in particular with a

Length / diameter ratio of 0.5-3.5, for receiving monomer (s) and / or catalysts and / or initiators) which are backmixable with already reacted product, and a discharge device (3), through which the reacted product from the mixing kneader (1) can be discharged, characterized in that the discharge device (3) is followed by another mixing kneader or extruder or flash pot (4), wherein between the discharge device (3) and extruder (4) a shredding device (18) for transferring product is switched on.

16. The apparatus according to claim 15, characterized in that the crushing device is a perforated plate (18).

17. The apparatus of claim 15 or 18, characterized in that the crushing device (18) is preceded by a pump, in particular a gear pump (17).

18. The device according to at least one of claims 15 to 17, characterized in that the gear pump (17) is preceded by a measuring device for continuous control of the constant product level in the mixing kneader.

19. The apparatus according to claim 18, characterized in that the gear pump (17) with a level gauge (8) in the first mixing kneader (1) is connected.

20. The apparatus of claim 18 or 19, characterized in that after the gear pump (17) and before the crushing device (18) there is the possibility of adding stripping agents or additives.

21. The device according to claim 20, characterized in that the stripping agent is water or nitrogen.